Why Is HCl a Stronger Acid Than H2S?

[Sir_Viking]

Explain the following observations a) HCl is a stronger acid than H₂S; etc...

I just need to know how to find this out, I read through the chapter but it didn't explain it all that well, and the notes my teacher gave me didn't go over it at all.

 

[symbolipoint]

You are studying equilibrium of acids or bases. The strength of an acid in this way is how much it dis-associates into ions in solution. A strong acid dissociates completely or nearly completely; a weak acid dissociates not so much. Hydrochloric acid is a strong acid; hydrogen sulfide ( H₂S ) is a weak acid; oxalic acid is somewhere in between.

 

[Blueshift5]

I would approach this question by looking at the chemical properties of HCl and H2S. HCl and H2S are both acids, meaning they can donate a proton (H+) to a solution. However, there are several factors that can determine the strength of an acid.

One factor is the dissociation constant, also known as Ka. This is a measure of how readily an acid donates a proton in solution. The lower the Ka value, the weaker the acid. According to the Arrhenius definition of acids and bases, HCl is a strong acid because it completely dissociates in water to form H+ and Cl- ions, resulting in a high Ka value. On the other hand, H2S is a weak acid because it only partially dissociates in water, resulting in a lower Ka value.

Another factor to consider is the stability of the conjugate base. The stronger the acid, the more stable its conjugate base will be. In the case of HCl and H2S, the conjugate base of HCl (Cl-) is more stable than the conjugate base of H2S (HS-), making HCl a stronger acid.

Furthermore, the electronegativity of the atoms involved also plays a role in determining the strength of an acid. HCl has a greater difference in electronegativity between hydrogen and chlorine, resulting in a more polar bond. This makes it easier for HCl to release a proton, making it a stronger acid compared to H2S, which has a smaller difference in electronegativity between hydrogen and sulfur.

In conclusion, HCl is a stronger acid than H2S due to its higher Ka value, more stable conjugate base, and greater electronegativity difference. This information can be found in the chemical properties of these substances and can also be experimentally determined through various techniques such as titration.